http://hdl.handle.net/2122/220 Wed, 22 May 2013 04:14:32 GMT 2013-05-22T04:14:32Z http://hdl.handle.net/2122/8663 Title: Integrating geologic fault data into tsunami hazard studies Authors: Basili, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Tiberti, M. M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Kastelic, V.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Romano, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Piatanesi, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Selva, J.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Lorito, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia Abstract: We present the realization of a fault-source data set designed to become the starting point in regional-scale tsunami hazard studies. Our approach focuses on the parametric fault characterization in terms of geometry, kinematics, and assessment of activity rates, and includes a systematic classification in six justification levels of epistemic uncertainty related with the existence and behaviour of fault sources. We set up a case study in the central Mediterranean Sea, an area at the intersection of the European, African, and Aegean plates, characterized by a complex and debated tectonic structure and where several tsunamis occurred in the past. Using tsunami scenarios of maximum wave height due to crustal earthquakes (Mw=7) and subduction earthquakes (Mw=7 and Mw=8), we illustrate first-order consequences of critical choices in addressing the seismogenic and tsunamigenic potentials of fault sources. Although tsunamis generated by Mw=8 earthquakes predictably affect the entire basin, the impact of tsunamis generated by Mw=7 earthquakes on either crustal or subduction fault sources can still be strong at many locales. Such scenarios show how the relative location/orientation of faults with respect to target coastlines coupled with bathymetric features suggest avoiding the preselection of fault sources without addressing their possible impact onto hazard analysis results. Thu, 18 Apr 2013 22:00:00 GMT http://hdl.handle.net/2122/8663 2013-04-18T22:00:00Z http://hdl.handle.net/2122/8323 Title: Deriving thrust fault slip rates from geological modeling: examples from the Marche coastal and offshore contraction belt, Northern Apennines, Italy. Authors: Maesano, F. E.; Toscani, G.; Dipartimento di Scienze della Terra e dell'Ambiente, Università di Pavia; Burrato, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Mirabella, F.; Dipartimento di Scienze della Terra, Università di Perugia; D'ambrogi, C.; ISPRA - Servizio Geologico d'Italia; Basili, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia Abstract: We present a reconstruction of the central Marche thrust system in the central-northern Adriatic domain aimed at constraining the geometry of the active faults deemed to be potential sources of moderate to large earthquakes in this region and at evaluating their long-term slip rates. This system of contractional structures is associated with fault-propagation folds outcropping along the coast or buried in the offshore that have been active at least since about 3Myr. The ongoing deformation of the coastal and offshore Marche thrust system is associated with moderate historical and instrumental seismicity and recorded in sedimentary and geomorphic features. In this study, we use subsurface data coming from both published and original sources. These comprise cross-sections, seismic lines, subsurface maps and borehole data to constrain geometrically coherent local 3D geological models, with particular focus on the Pliocene and Pleistocene units. Two sections crossing five main faults and correlative anticlines are extracted to calculate slip rates on the driving thrust faults. Our slip rate calculation procedure includes a) the assessment of the onset time which is based on the sedimentary and structural architecture, b) the decompaction of clastic units where necessary, and c) the restoration of the slip on the fault planes. The assessment of the differential compaction history of clastic rocks eliminates the effects of compaction-induced subsidence which determine unwanted overestimation of slip rates. To restore the displacement along the analyzed structures, we use two different methods on the basis of the deformation style: the fault parallel flow algorithm for faulted horizons and the trishear algorithm for fault-propagation folds. The time of fault onset ranges between 5.3-2.2 Myr; overall the average slip rates of the various thrusts are in the range of 0.26-1.35 mm/yr. Mon, 31 Dec 2012 23:00:00 GMT http://hdl.handle.net/2122/8323 2012-12-31T23:00:00Z http://hdl.handle.net/2122/8236 Title: Morphometric analysis in the offshore of the southern Taranto Gulf: unveiling the structures controlling the Late Pleistocene-Holocene bathymetric evolution Authors: Santoro, Enrico; Dipartimento di Scienze della Terra, Università degli Studi di Napolii Federico II, Napoli; Ferranti, Luigi; Dipartimento di Scienze della Terra, Università degli Studi di Napolii Federico II, Napoli; Passaro, Salvatore; Istituto per l’Ambiente Marino Costiero, Consiglio Nazionale delle Ricerche, Napoli; Burrato, Pierfrancesco; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Morelli, Danilo; Dipartimento di Scienze Geologiche, Ambientali e Marine, Università di Trieste Editors: Critelli, Salvatore; Muto, Francesco; Perri, Francesco; Petti, Fabio Massimo; Sonnino, Maurizio; Zuccari, Alessandro Abstract: The present study is focused on a morphometric analysis of high resolution multibeam data (10m, 5m and, locally, 2m resolution), that were acquired during the oceanographic TEATIOCA 2011 campaign along a sector of the Ionian margin of northern Calabria. The integration of morphometric analysis with sparker and chirp data allowed to unveil basic but robust information about: 1. hierarchy of the fault systems controlling the bathymetric evolution; 2. the interplay between tectonic and erosional processes in sea-floor modeling; 3. uplift rates; 4. tilting processes. Mon, 17 Sep 2012 22:00:00 GMT http://hdl.handle.net/2122/8236 2012-09-17T22:00:00Z http://hdl.handle.net/2122/8234 Title: Geometry and modeling of an active offshore thrust-related fold system: the Amendolara Ridge, Ionian Sea, southern Italy Authors: Ferranti, Luigi; Dipartimento di Scienze della Terra, Università degli Studi di Napolii Federico II, Napoli; Pepe, Fabrizio; Dipartimento di Scienze della Terra e del Mare, Università di Palermo; Burrato, Pierfrancesco; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Santoro, Enrico; Dipartimento di Scienze della Terra, Università degli Studi di Napolii Federico II, Napoli; Mazzella, Maria Enrica; Dipartimento di Scienze della Terra, Università degli Studi di Napolii Federico II, Napoli; Morelli, Danilo; Dipartimento di Scienze Geologiche, Ambientali e Marine, Università di Trieste; Passaro, Salvatore; Istituto per l’Ambiente Marino Costiero, Consiglio Nazionale delle Ricerche, Napoli; Vannucci, Gianfranco; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia Editors: Critelli, Salvatore; Muto, Francesco; Perri, Francesco; Petti, Fabio Massimo; Sonnino, Maurizio; Zuccari, Alessandro Abstract: On the Ionian Sea coast of southern Italy, spanning the transition from the Calabrian Arc to the Apennines, NE-directed motion of the thin-skinned frontal thrust belt of the Apennines toward the Apulian foreland reportedly ceased during the Early-Middle Pleistocene. The submarine extension of the frontal thrust belt is represented by the Amendolara ridge, which stretches for over 80 km to the SE beneath the Taranto Gulf. High-resolution marine geophysical data collected on the Amendolara ridge during the TEATIOCA_2011 cruise provided unequivocal constraints to assert active fault-related fold growth. Single-channel seismic (sparker) and acoustic CHIRP profiles, corroborated by multibeam mapping and shallow coring, form the novel dataset to constrain the near-bottom evolution. The new data were benchmarked to the crustal geometry by means of interpretation of existing multichannel seismic profiles. Mon, 17 Sep 2012 22:00:00 GMT http://hdl.handle.net/2122/8234 2012-09-17T22:00:00Z http://hdl.handle.net/2122/8226 Title: The deformation offshore of Mount Etna as imaged by multichannel seismic reflection profiles Authors: Argnani, A.; CNR, ISMAR-Bologna, Bologna, Italy; Mazzarini, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; Bonazzi, C.; CNR, ISMAR-Bologna, Bologna, Italy; Bisson, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; Isola, I.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia Abstract: Despite the clear evidence of active flank dynamics that is affecting the eastern side of Mount Etna, the contribution of tectonic processes has not been yet understood. So far, the various models proposed to explain the observed flank deformation have been based on onshore structural data, coming from the volcanic edifice. The Ionian offshore of Mount Etna has been only recently investigated using multichannel seismic profiles, and offers the opportunity to image the structural features of the substrate of the unstable flank of the volcano. This contribution aims at describing the deformation located offshore Mount Etna using multichannel seismic profiles recently acquired during three seismic surveys. The onshore flank deformation of Mount Etna appears to be laterally confined by two tectonic guidelines, trending roughly E–W, located to the north and south of the deforming flank; the northern guideline, in particular, takes the surface expression of a sharp fault (Pernicana Fault). Though often assumed that these boundary structures continue offshore as linear features, connected to a frontal thrust ramp, the occurrence of this simple offshore structural system has not been imaged. In fact, seismic data show a remarkable degree of structural complexity offshore Mount Etna. The Pernicana Fault, for instance, is not continuing offshore as a sharp feature; rather, the deformation is expressed as ENE–WSW folds located very close to the coastline. It is possible that these tectonic structures might have affected the offshore of Mount Etna before the Pernicana Fault system was developed, less than 15 ka ago. The southern guideline of the collapsing eastern flank of the volcano is poorly expressed onshore, and does not show up offshore; in fact, seismic data indicate that the Catania canyon, a remarkable E–W-trending feature, does not reflect a tectonic control. Seismic interpretation also shows the occurrence of a structural high located just offshore the edifice of Mount Etna. Whereas a complex deformation affects the boundary of this offshore bulge, it shows only limited internal deformation. Part of the topography of the offshore bulge pre-existed the constructional phase of Mount Etna, being an extension of the Hyblean Plateau. Only in the northern part, the bulge is a recent tectonic feature, being composed by Plio-Quaternary strata that were folded before and during the building of Mount Etna. The offshore bulge is bounded by a thrust fault that can be related to the intrusion of the large-scale magmatic body below Mount Etna. Mon, 31 Dec 2012 23:00:00 GMT http://hdl.handle.net/2122/8226 2012-12-31T23:00:00Z http://hdl.handle.net/2122/8090 Title: Geological evidence for paleotsunamis along eastern Sicily (Italy): an overview Authors: De Martini, P. M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Barbano, M. S.; Dipartimento di Scienze Biologiche, Geologiche e Ambientali, Università di Catania, Italy; Pantosti, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Smedile, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Pirrotta, C.; Dipartimento di Scienze Biologiche, Geologiche e Ambientali, Università di Catania, Italy; Del Carlo, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; Pinzi, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia Abstract: We present geological evidence for paleotsunamis along the 230 km-long coast of eastern Sicily (Italy); combining this information with historical data, we reconstruct a unique history of tsunami inundations. We integrate data on 38 paleotsunami deposits (from fine sand layers to boulders) collected at 11 sites (one offshore). The geological data record traces of large tsunamis which have occurred during the past 4 millennia. Chronological constrains include 14C, 210Pb and 137Cs, OSL and tephrochronology. When compatible, the age of the paleotsunami deposits is associated to historical events, but it is also used to highlight unknown tsunamis. Average tsunami recurrence interval (between 320 and 840 yr) and minimum inland tsunami ingressions (often greater than the historical ones) were estimated at several sites. On the basis of this work, the tsunami catalogue is implemented by two unknown tsunamis which occurred during the first millennium BC and by one unknown regional tsunami, which occurred in 650–770 AD. By including this latter event in the eastern Sicily catalogue, we estimate an average recurrence interval for strong tsunamis of ca. 385 yr. Comparison and merging of historical and geological data can definitely contribute to a better understanding of regional and local tsunami potential and provides robust parameters to be used in tsunami hazard estimates. Mon, 13 Aug 2012 22:00:00 GMT http://hdl.handle.net/2122/8090 2012-08-13T22:00:00Z http://hdl.handle.net/2122/8088 Title: Combining inland and offshore paleotsunamis evidence: the Augusta Bay (eastern Sicily, Italy) case study Authors: Smedile, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; De Martini, P. M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Pantosti, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia Abstract: Offshore and inland geological evidence for multiple tsunami inundations was found in the Augusta Bay area: (1) the main local historical tsunamis (1908, 1693, 1169), (2) two far-generated tsunamis (i.e. Crete 365AD and Santorini, 3600 BP), and (3) seven unknown tsunamis). Average tsunami recurrence intervals from inland and offshore investigations of about 550 and 320 yr, respectively were obtained for the past 4 ka. The history of paleotsunamis from the marine record appears to be as complete as the historical one for the past millennium, yielding an average tsunami recurrence interval of 250 yr for the Augusta Bay. Geological data allow also estimating a minimum tsunami inundation distance of 530m and a minimum run-up of 5 m. The marine record contains evidence for more paleotsunamis with respect to the inland one because of continuous sedimentation and better preservation of stratigraphy in the offshore with respect to coastal areas, which are commonly affected by intermittent-erosion and sedimentation and anthropic activities. This work shows that the integration of geological and historical data can provide critical information regarding the extent and age of tsunamis of the past (e.g. inundation distance, age, and frequency), which is of immediate relevance for tsunami hazard assessment. Mon, 13 Aug 2012 22:00:00 GMT http://hdl.handle.net/2122/8088 2012-08-13T22:00:00Z http://hdl.handle.net/2122/8039 Title: Magnetic and seismic reflection study of Lake Cheko, a possible impact crater for the 1908 Tunguska Event Authors: Gasperini, L.; CNR-Ismar Bologna; Cocchi, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Stanghellini, C.; INAF-Bologna; Stanghellini, G.; CNR-Ismar Bologna; Del Bianco, F.; CNR-Ismar Bologna; Serrazanetti, M.; CNR-Ismar Bologna; Carmisciano, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: A major explosion occurred on 30 June 1908 in the Tunguska region of Siberia, causing the destruction of over 2,000 square km of taiga; pressure and seismic waves detected as far as 1,000 km away; bright luminescence in the night skies of Northern Europe and Central Asia; and other unusual phenomena. This “Tunguska Event” is probably related to the impact with the Earth of a cosmic body that exploded about 5-10 km above ground, releasing in the atmosphere 10-15 Mton of energy. Fragments of the impacting body have never been found, and its nature (comet or asteroid) is still a matter of debate. We report here results from a magnetic and seismic-reflection study of a small (~500 m diameter) lake, Lake Cheko, located about 8 km NW of the inferred explosion epicenter, that was proposed to be an impact crater left by a fragment of the Tunguska Cosmic Body. Seismic-reflection and magnetic data revealed a P-wave velocity/magnetic anomaly close to the lake center, about 10 m below the lake floor; this anomaly is compatible with the presence of a buried stony object and supports the impact crater origin for Lake Cheko. Fri, 11 May 2012 22:00:00 GMT http://hdl.handle.net/2122/8039 2012-05-11T22:00:00Z http://hdl.handle.net/2122/8034 Title: Birth of an ocean in the Red Sea: Initial pangs Authors: Ligi, M.; CNR-ISMAR Bologna; Bonatti, E.; CNR-ISMAR Bologna; Bortoluzzi, G.; CNR-ISMAR Bologna; Cipriani, A.; CNR-ISMAR Bologna; Cocchi, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Caratori Tontini, F.; GNS Science; Carminati, E.; Università di Roma "La Sapienza"; Ottolini, L.; CNR -Pavia; Schettino, A.; Università di Camerino Abstract: We obtained areal variations of crustal thickness, magnetic intensity, and degree of melting of the sub- axial upwelling mantle at Thetis and Nereus Deeps, the two northernmost axial segments of initial oceanic crustal accretion in the Red Sea, where Arabia is separating from Africa. The initial emplacement of oceanic crust occurred at South Thetis and Central Nereus roughly $2.2 and $2 Ma, respectively, and is taking place today in the northern Thetis and southern Nereus tips. Basaltic glasses major and trace element com- position suggests a rift-to-drift transition marked by magmatic activity with typical MORB signature, with no contamination by continental lithosphere, but with slight differences in mantle source composition and/or potential temperature between Thetis and Nereus. Eruption rate, spreading rate, magnetic intensity, crustal thickness and degree of mantle melting were highest at both Thetis and Nereus in the very initial phases of oceanic crust accretion, immediately after continental breakup, probably due to fast mantle upwelling enhanced by an initially strong horizontal thermal gradient. This is consistent with a rift model where the lower continental lithosphere has been replaced by upwelling asthenosphere before continental rupturing, implying depth-dependent extension due to decoupling between the upper and lower lithosphere with man- tle-lithosphere-necking breakup before crustal-necking breakup. Independent along-axis centers of upwell- ing form at the rifting stage just before oceanic crust accretion, with buoyancy-driven convection within a hot, low viscosity asthenosphere. Each initial axial cell taps a different asthenospheric source and serves as nucleus for axial propagation of oceanic accretion, resulting in linear segments of spreading. Fri, 17 Aug 2012 22:00:00 GMT http://hdl.handle.net/2122/8034 2012-08-17T22:00:00Z http://hdl.handle.net/2122/7958 Title: Project S1: Analysis of the seismic potential in Italy for the evaluation of the seismic hazard Authors: Barba, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Doglioni, C.; Sapienza Università di Roma Abstract: The project S1 was aimed at (a) collecting new data and to update the existing databases needed to quantify seismic hazard; (b) promoting new studies on specific fields of knowledge and less-explored areas of Italy; (c) testing new approaches to evaluate seismic potential; (d) bounding slip rate values to use within probabilistic hazard estimates; and (e) preparing the way towards a future seismic hazard map of Italy. It was designed with three scientific parts – nationwide basic data, rheology, and field studies – and implemented into four tasks: 1) earthquake geodesy and modeling, 2) seismological data and earthquake statistics, 3) earthquake geology, and 4) tsunamis. Although with many difficulties and some delay, described in the appropriate section, all the above objectives have generally been accomplished. New observations were collected through original fieldwork and more sophisticated analyses were performed on existing data. Datasets needed for the seismic hazard estimates were updated at various levels by reducing both epistemic and aleatory uncertainties. New studies were carried out on specific fields of knowledge, e.g. addressing the repeatability of geodetic and stress data measurements or the seismogenic behavior of misoriented faults. Studies on less-explored areas were stimulated, and faults, whose seismic potential was not previously accounted for, were mapped and/or parameterized in the Ionian and Adriatic Seas, in Calabria, Sicily and the Southwestern Alps. Independent approaches to evaluate the seismic potential were tested, and a large effort toward homogenization and verifiability was made. The substantial improvements of nationwide datasets and understanding of the tectonic processes in large areas of the country set the basis for a significantly better assessment of seismic hazard. Tue, 29 Jun 2010 22:00:00 GMT http://hdl.handle.net/2122/7958 2010-06-29T22:00:00Z